I. Field of the Invention
The invention relates to devices used for cutting long sections of sheet material. Particularly material such as gypsum wall board which is relatively stiff and supplied usually in sections four feet wide and up to sixteen feet long. It is often necessary to cut sheets of this type into narrower sections for use in building construction. This is commonly accomplished by marking the boards using rulers, squares and other straight edges. It involves marking at several points down from the edge of the sheet, drawing straight lines along the material from marker to marker and then scoring the material with a knife along the lines. Lastly the desired panel is broken loose. The task requires using several "tools" consecutively picking up one, placing it down, then the other etc. The tools must be kept in hand and delays can be encountered when one of the several tools is missing or moved a distance away from the last.
II. Description of the Prior Art
U.S. Pat. No. 3,439,426 granted to R. Wilson Apr. 22, 1969 discloses a glass-cutting tool employing a T square. The tongue of the T square is bifurcated and a cutter head is slidable along the tongue to score the upper surface of a sheet of glass. In use the starting point of the score is located by use of a ruled head of the T square. The T square then is positioned with its head at the proper point and the cutter is slid along the tongue of the T square. This device does not provide a means for scoring an elongated sheet parallel to its edge as is needed for use in construction with material such as gypsum wallboard. It provides only for scoring laterally inwardly from an edge.
U.S. Pat. No. 4,030,195 granted June 21, 1977 to Thomas Insolio discloses a scoring device which is adapted for scoring sheets which rest on a table and wherein the tool has access to the table top surface on which the material lies. The tool comprises a cam plate which is a quadrilateral having four sides of unequal lengths. The cam is adapted to be slid along the table while it also slides along against the side edge of the sheet to be cut. A rod extends perpendicularly to the cam and carries a cutting tool which extends downwardly to cut the material as the tool is slid along. The height of the cutting tool above the surface of the table can be adjusted by rotating the cam. Since there are four edges to the cam i.e. four sides, there are four different heights at which the tool can be placed thus limiting the use of the tool. In Insolio a rod is positioned a substantial distance above the sheet to be scored and the cam-like block must be held against one edge of the material while it is also pressed down against the table at the same time in order to prevent canting of the cutting tool. The tool is likely to prove unstable particularly as the distance between the cutting edge and the cam block increases. The cutter depends downwardly from the elongated rod. In addition to the tendency of the rod to flex and the cam to sway the cutter does not provide stability longitudinally transverse of the single rod support. Thus flexing, bending and twisting leading to inaccuracies are a constant danger.